ML20245C698
| ML20245C698 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 06/19/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20245C696 | List: |
| References | |
| NUDOCS 8906260255 | |
| Download: ML20245C698 (5) | |
Text
I pS KEQ UNITED STATES J,
g NUCLEAR REGULATORY COMMISSION v
,p*
7,,
j WASHINGTON, D. C. 20555 j
k*****,/
f
]
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.130 TO FACILITY OPERATING LICENSE NO. OPR-32 AND AMENDMENT NO.130 TO FACILITY CPERATING LICF,NSE NO. DPR-37 VIRGINIA ELECTRIC AND POWER COMPANY-SURRY POWER STATION, UNIT NOS.1 AND 2 DOCKET N05. 50-280 AND 50-281 l^
1.0 INTRODUCTION
The service water (SW) system at Surry,. Units 1 and 2, is unique when' compared to the SW systems at most nuclear power plants. Rather than emergency service water (ESW) system pumps forcing flow through the. component cooling water (CCW)-
i system and other safety-related system heat exchan l
gravity feed from a high level intake canal.'(HLIC)gers, flow is induced via which is required to.have a
~
.certain level of water to provide' adequate head in order to meet minimum flow -
requirements. However, tha inventory in the intake canal is~not sufficient to.
meet long-term cooling requirements, and, therefore, three diesel-driven ESW '
pumps (actually makeup pumps) are provided to_ replenish the canal inventory in j
an emergency. During-normal o circulating water system (CWS)peration, canal ' inventory is maintained by the pumps, which also act as makeup pumps. The CWS.
'l flow through the main condensers is also gravity. flow from the intake canal.
The ESW and CWS pumps take suction from the James River.
As a result of a Safety System Functional Inspection (SSFI) during the weeks of September 12 and September 2r, 1988, the NRC staff identified several-concerns regarding the operabiUN of the SW' system that were directly related j
to the unique Surry SW system c.. ign. Following the identification of these i
concerns, the licensee re-evaluated the design basis for the SW system,'partic-ularly with respect to HLIC inventory) control and management following a '
4 postulateddesignbasisaccident(DBA.
AL a result of this re-evaluation,
)
the licensee, by lettet dated March 27, 1989, identified design modifications and proposed Technical Specification changes necessary to correct deficiencies i
found'during the SSFI and followup re-evaluation.. The following' evaluation addresses the design modifications and' proposed Technical Specification changes identified in the licensee's March 27, 1989 submittal.
i 2.0
,E_ VALUATION' J
The licensee has proposed three modifications to the plant Technical Specifi-cations.- These changes will 1.
Raise the minimum required HLIC level from 18 feet to 23 feet, i
j P
l.
^
X 1
j j
s.
3, o
c 3 3 l '
2.
Increase the requirement from two to three ESW pumps to be operable with provisions for limited duration maintenance outages, and 3.
Provide operability and surveillance requirements for the new safety-related HLIC: level actuation. system.
The proposed Technical Specification (TS) changes are accompanied by design j
modifications which include new vacuum breakers to prev 6nt reverse siphoning
)
at the new, higher canal-level ('23 feet), addition of a safety-related canal low level acuub ionL system, Lrepowering the circulating water. system valves to assure isolation in the. event of an emergency. diesel generator failure, installation of manual vacuum breaker valves on the discharge tunnel to break prime and hence conserve inventory, and installation of CCW heat exchanger SW flow instrumentation to allow throttling during a DBA.
q j
The licensee's re-evaluation ~ identified six ba' sic deficiencies which precipitated the proposed TS changes, design modifications and associated changes to station procedures as described below.
The first deficiency 'was related to HLIC level drawdown during a DBA'due to a..
single failure. The DBA is assumed to be a loss of: coolant accident (LOCA) and a loss of off-site power (LOOP).
Possible single failure problems ' included
{
an ESW pump failure, emergency diesel generator failure, and a failure to close any one of.~ the isolation-valves to heat exchangers not essential for-post-DBA.-
heat removal. To resolve this issue, amergency operating procedures
- EOPs) were revised for operation of ESW pumps.and SW heat exchangers, and require manual confirmation / action for closing specific SW isolation valves.; Design modifications were also made to repower the CWS isolation valves, as required, to at least one CWS inlet or outlet valve for each condenser waterbox in order to ensure isolation following any single failure.
In addition, to allow time i
for operator action, the TS would be revised to raise the minimum intake canal level from IB feetL to 23 feet.
The second deficiency noted was reliance on nonsafety-related signals for the main condenser and SW isolation valves.
To resolve this concern, a safety-related canal low level actuation system was installed to provide i
safety-related signals to the system isolation valves. TS changes were also proposed to add operability and surveillance requirements for the new safety-related instrumentation.
A third deficiency was the potential for inadequate ESW supply'(makeup) during a DBA in one unit with cooldown of the other unit or residual-heat removal-(RHR)-system operation in the nonaccident unit (within a certain time ' interval-i following shutdown based on decay heat production).
To resolve this problem.
TS changes were proposed to (1) require three ESW pumps to be operable with two l
units at power, and (2) require three ESW pumps to be operable'with one unit'at power when heat loads from the spent fuel pool and a. shutdown unit ~ are equal to.
I or greater than 25 million BTU /hr. The present TS only require the operability of:two ESW pumps.:
. A fourth deficiency was the potential for the CWS pump discharge lines to siphon back to the James. River on loss of the CWS pumps. The' present. design' contains a passive vacuum _ breaker ~uesigned to prevent siphoning below a. canal
-level of 19 feet, which is. consistent with the present specified level'of
_.-__l_...-_.--__..----._-.-__.~___--__
.--._I.-
I!
+
s.
i 18 feet in the TS. However, in order to be consistent with the proposed TS level of 23 feet, ncw passiva vacuum breakers have been installed to assure a reverse siphon will not be present for canal. levels less than or equal to l
23 feet. The new vacuum breaker is located just above the 23 foot level.
The fifth deficiency identified by the licensee was the inability %f she SW system to meet the requirements of Appendix. R to 10 CFR Part 50 regarding l
safe shutdown following a fire. The current Appendix R analysis allows for failure of the CWS isolation valves to close followed by operator action.
However, a method for breaking condenser vacuum under full flow conditions is t!
not addressed in the current design. The resolution of this. deficiency. involves 1
the installation of vacuum breakers on the condenser water b' oxes. The vacuum
)
breakers will have pneumatic remote and local capability.- The' remote control stations are required in the event of a fire in the turbine building, and are located in a' fire area that is appropriately separated-from the turbine building by a fire wall. in accordance with Appendix R criteria.
(
)
The sixth and final. major deficiency tdentified byf the licensee involved CCW heat exchnger operability in a degraded condition. The SW system side 'of the heat:
exchangers is' subject to significant microfouling and macrofouling phenomena.
j The possibility of reduced performance of the heat exchangers must be accounted for. in the design basis by application of appropriate fouling factors to both the SW and CCW modes of the heat exchangers.. The resolution of:this concern 3
involves a combination of design modifications procedural changes and
.i periodic testing as follows:
1.
The installation of du ferential pressure instrumentation on the SW side-of the heat exchangers.
2.
The installation of discharge tunnel vacuum breakers to conserve HLIC inventor valves (y for use in the CCW heat exchangers. These are safety-related :
manually operated) which may have to be operated within '4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> 1
after a DBA if the discharge tunnel self-priming action'is not already l
bro ken.
3.
The implementation of a periodic test to measure combined CWS and SW system isolation valve leakage and a periodic test to measure CCW heat exchanger operability. The leakage test is required to demonstrate that valve.
leakage (HLIC inventory loss) is less than that assumed in canal inventory-analysis following a DBA. Due to the seasonal variations in heat exchanger fouling, the period for the CCW heat exchanger operability test must be j
established by first setting a fairly high testing frequency until a 4
reduction in that frequency. can be substantiated.
A number of other potential design and operating deficiencies were identified.
1 by the licensee, which were related to the ESW pumps and pumphouse. Appropriate a
actions have been'taken by the-licensee to correct these potential deficiencies.
i These actions include design modifications, maintenance and testing procedural.
changes and additional instrumentation. These changes and modifications are l
L conservative in nature and should make the;ESW pumps more reliable.
i I
l
__ -.___:._ ___-___ ___ ____ - _ _ _ _ n
1 f '* $.
l
, I The licensee has proposed two TS changes to TS 3.14 " Circulating and Service Water Systems." The first would increase the minimum required HLIC level to i
1 support SW heat exchanger flow by allowing for automatic and operator action times to isolate nonessential SW system flowpaths. The second proposed change to TS 3.14 requires three operable ESW pumps for HLIC makeup for long-term l
accident mitigation. Both of these proposed changes are more conservative than the original TS and are required to meet the design basis of the SWS as reanalyzed by the licensee. The revised design basis includes the most limiting DBA coupled with any single active feilure.
1 A third TS change revises both TS 3.7 and 4.1 related to the engineered safety j
featttcs (ESF) instrumentation setpoints, action requirements and testing j
frequencies. These TS changes are required to be consistent with the design 1
modifications which included a safety-related intake canal level actuation l
system. The setpoints are consistent with the revised design basis and proposed changes to TS 3.14.
The action statements and testing frequencies are consistent with those for other ESF instrumentation-in the Surry plant TS.
The licensee has also revised the Bases Section of the plant TS to be j
consistent with the proposed TS changes and design modifications.
1 The design modifications described above are considered by the staff to be safety improvements, and provide added assurance that adequate canal inventory 4
will be available and maintained to cope with the worst-case DBA coupled with 1
any single active failure. These modifications improve'the SW system post-accident capability for both the short and long term.
3.0
SUMMARY
f As described above, the staff has reviewed and evaluated the licensee's design
]
modifications and associated proposed TS changes related to the SW system and HLIC managtment. Based on its review, the staff concludes that the SW system and intake. canal design modifications will ensure that the revised design basis is satisfied and meet the following staff criteria:
1.
General Design Criterion (GDC) 2, " Design Bases for Protection Against Natural Phenomena," as it relates to protection of the cooling water system against earthquakes and tornadoes.
2.
GDC 44, " Cooling Water," as it relates to providing adequate cooling I
requirements under both normal and accident conditions, suitable redundancy, and the capability to isolate nonessential systems, components or piping if required; and Regulatory Guide 1.27. " Ultimate Heat Sinks for Nuclear Power Plantsy" as it relates to provisions for a reliable long-term source of cooling water to mitigate.an accident in one unit and ensure a safe cold shutdown of the other unit.
3.
GDC 45, " Inspection of Cooling Water Systems," as it relates to provisions to permit inservice inspection of safety-related cooling water system components and equipment.
I 4
GDC 46, " Testing of Cooling Water Systems," as it re16tes to design provisions to permit operational functional testing of safety-related cooling water system components and equipment.
.?
e
- e The staff further concludes that the proposed TS changes are more conservative than the current specifications and are consistent with the design modifications dnd revised design basis analyses. The staff, therefore, concludes that the design modifications and proposed TS changes are acceptable.
4.0 ENVIRONMENTAL CONSIDERATION
Pursuar.t to 10 CFR 51.21, 51.32 and 51.35, an environmental assessment and finding of no significant impact have been prepared and published in the Federal Register on June 19,1989 (54 FR 25761). Accordingly, based upon the ip71ronmental assessnent, the Commission has determined that the issuance of the amendments will not have a significe nt effect on the quality of the human environment.
5.0 CONCLUSION
We have concluded, based on the considerations discussed above, that:
(1 ) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed venner, and (2) such activities will be conducted in compliance with the Commission's regulations and the issuance of these amendments will not be inimical to the common defense and security or to the health and safety of the public.
Dated: June 19,1989 Principal Contributor:
W. LeFave S
a
______-___